1. Field of the Invention
This invention relates generally to chip packaging and particularly to chip packaging including a heat sink.
2. Related Art
An electronic component (e.g., a Central Processing Unit) may generate a significant amount of heat when operating. If not dissipated in time, this heat can degrade performance of the component. To dissipate some of the generated heat, a heat sink device is commonly placed in contact with the component. The heat sink device usually includes a plate and several protrusions from the plate that increase the heat transfer surface area. Sometimes, a fan is used in addition to the heat sink device to assist in heat dissipation.
Currently, a number of methods are used to fasten the heat sink device to the component. FIG. 1 depicts an exemplary clip 10 disclosed in U.S. Pat. No. 6,153,932, which is incorporated by reference herein. Clip 10 includes a rectangular frame 12 with a hole 14. Rectangular frame 12 has protruding portions that are designed to extend through a hole, such as side plates 16 and protruding rods 20. Side plates 16 include a first side plate 16a connected to one part of rectangular frame 12 and a second side plate 16b connected to a different part of rectangular frame 12. Each of side plates 16a and 16b may have fastening hooks 18a and 18b, respectively. Side plates 16a and 16b press against two outer edges of a heat sink and a component, and fastening hooks 18a and 18b snap onto the bottom edges of the component. Protruding rods 20 may include a first protruding rod 20a and a second protruding rod 20b connected to the sides of frame 10 that do not have a side plate. Clip 10 may also have elastic rods 22 protruding from the inner side walls of frame 10 into hole 14 to provide extra stability and attachment to a heat sink. A person of ordinary skill in the art would understand that other structures for clip 10 are possible. For example, frame 12 and hole 14 may be of any other polygonal shape or even a circular shape. Furthermore, clip 10 may include any fastening device, such as a screw or a snap feature, that can be used to hold a heat sink in a fixed position relative to a component.
However, the currently used methods usually impose at least one limitation on the design of the motherboard or the heat sink. For example, while a screw allows flexibility in the dimensions of the heat sink, it requires that the motherboard have holes. A clip of the sort shown in FIG. 1 does not require that a motherboard have holes, but requires that heat sink and the component have a width substantially equal to the width of the clip. Such limitations compromise design optimization of heat sink devices.
A heat sink device that provides flexibility in terms of both the size of the heat sink and the motherboard circuitry design is needed.
In accordance with the present invention, a heat sink extends beyond all outer boundaries of a component cooled by the heat sink. Such an oversized heat sink allows better optimization of heat transfer values than a conventional heat sink, which usually has at least one dimension (e.g. width as noted above) the same as or substantially equal to the corresponding dimension of the component to be cooled. An oversized heat sink attached by a clip to an electronic component not only allows better optimization of heat transfer values but also provides greater flexibility for motherboard circuitry design than a conventional heat sink.
In one embodiment, the heat sink has at least one cutout (or hole) shaped and located so that a portion (hereinafter xe2x80x9cprotruding portionxe2x80x9d) of a clip can extend from one surface of the heat sink and mechanically fasten the electronic component to another (eg., the opposite) surface of the heat sink. The cutout (or hole) may be shaped to fit around the protruding portion. For example, if the protruding portion is a flat plate, the cutout (or hole) through which the protruding portion is inserted may be a rectangular slit. If the protruding portion is a rod, the cutout (or hole) may be circular-shaped. The clip may fasten the heat sink to the component by the protruding portion snapping onto one or more edges of the component. When the clip fastens the heat sink to the component, no hole is needed in the motherboard. In an alternative embodiment, the clip may fasten a component to a heat sink by two or more protruding portions attaching to a motherboard and sandwiching the component between the heat sink and the motherboard. In this alternative embodiment, protruding portions of the clip extend not only through a cutout in the heat sink but also through a cutout in the motherboard, and each snaps onto an edge of the hole in the motherboard.
The clip may include a polygonal (e.g., rectangular) frame with a hole in the middle and a protruding portion on each side of the polygonal frame. Since cutouts (or holes) can be located anywhere on the heat sink, such cutouts (or holes) provide flexibility in terms of the size of the heat sink that can be used with a standard sized clip, and the location on the heat sink where the component is fastened. For example, locating cutouts away from the edges of the heat sink results in a component being fastened near the center of a heat sink. In some embodiments the heat sink extends beyond all outer boundaries of the component, although this is not required in other embodiments.